Biomedical subjects
Publications and source records attributed to X F Dai.
A series of 3-(1H-benzimidazole-2)-2-propenoic acid derivatives were prepared and tested for schistosomicidal activity. The acid was proved to be a cis-isomer. Preliminary pharmacological tests showed that these compounds were in effective.
Nuclear area and orientation in the subventricular and intermediate zones was studied quantitatively in coronal vs. sagittal sections of the dorsomedial neocortex. Nissl-stained methacrylate-embedded normal rat embryos were studied between embryonic days (E) 13 and E22. The area of nuclear profiles and the degrees their long axes (defined as a straight line through the two most distant points in the nuclear profile) deviated from the horizontal (defined as parallel to the pial membrane) were determined with a computer-graphics program. Because the nucleus is the most clearly outlined structure in embryonic cells, the area and orientation of the nucleus was taken to reflect the overall size and orientation of the cell body. Nuclear area is larger in the coronal plane than it is in the sagittal plane, especially between E17 and E20. Cell body orientation in the subventricular and lower intermediate zones is predominantly horizontal in the coronal plane and predominantly vertical in the sagittal plane. In the upper intermediate zone, cell body orientation is predominantly vertical in both planes, but more so in the sagittal plane. These data indicate that the majority of cell bodies in the subventricular and lower intermediate zones have a horizontally oriented, flattened elliptical shape with their larger diameters lying within the coronal plane and their smaller diameters in the sagittal plane. Because of the flattening, the cell bodies falsely appear to be vertically oriented in the sagittal plane. Qualitative observations in horizontal sections confirmed the quantitative computer analysis. These results are related to other findings with [3H]thymidine autoradiography concerning cell migration and the sojourn of cells in the subventricular and intermediate zones.
Three-dimensional reconstructions of the normal rat embryonic (E) neocortex on days E15, E17, E19, and E21, using Skandha (software designed by J. Prothero, University of Washington, Seattle), show that the neocortical ventricular zone shrinks rapidly in the medial direction during cortical morphogenesis. [3H]thymidine autoradiography indicates that the shrinkage of the ventricular zone occurs before neurons in lateral and ventrolateral parts of layers IV-II are generated. Consequently, most of these neurons originate 400-1000 microns medial to their settling sites in the cortical plate. Embryos killed at daily intervals up to E21 after a single injection of [3H]thymidine on either E17 or E18 revealed the presence of a prominent migratory path, the lateral cortical stream, used by neurons migrating to the lateral and ventrolateral cortical plate; neurons migrating to the dorsal cortical plate follow a direct radial path. Arrival times of neurons in the cortical plate depend on the migratory path and are proportional to the overall distance travelled. Neurons that migrate only radially arrive in the dorsal cortical plate in two days (shortest route). Neurons that migrate laterally arrive in the lateral cortical plate in 3 days (longer route) and in the ventrolateral cortical plate in 4 days (longest route). [3H]thymidine autoradiography also shows that cells generated in the neocortical ventricular zone migrate in the lateral cortical stream for 5 or more days and accumulate in a reservoir. Cells leave the reservoir to enter the piriform cortex and destinations (as yet undetermined) in the basal telencephalon. The lateral cortical stream is found wherever the neocortical primordium surrounds the basal ganglia and is absent behind the basal ganglia. A computer analysis of nuclear orientation in anterior and posterior parts of the intermediate zone in the dorsal neocortex between days E17 and E22 shows that horizontally oriented nuclei are more common anteriorly where many cells are migrating laterally than posteriorly where most cells are migrating radially.
Dentine of 27 permanent human teeth was examined by scanning electron microscopy. The teeth were incisors, canines, premolars and molars, ranging in age from 18 to 54 yr. Intratubular collagen was found in 65% of the dental tubules in inner dentine (closest to the pulp) with 16% of the tubules containing large collagen bundles occupying more than one-fifth of the lumen. In middle dentine the corresponding figures were 42 and 7%, and for outer dentine, 12 and 0% This pattern of distribution was the same for all tooth families examined and appeared to be unrelated to age.